I weight 73 Kg and 5'8" my other kite board is a Firewire kite version Hellfire 5'6" with 24.5L my plan is to keep the Vanguard 5'4" as my light wind board (12 to 17 knots) and replace the Hellfire with a bigger board but less volume for higher wind (20+ knots range) I'm thinking on a Tyrant 5'8" (22L). Both probably I would buy the Tyrant and keep the Hellfire because is a really nice board and is a bomb proof board.
The Vanguard 5'4" have basically the same volume of the Whip 25.9L vs 26L but in theory the Vanguard would go early because is a MPH (Modern Planing Hull). I was thinking 5'2" or 5'4" and I order the 5'4" thinking more on the low wind benefits so probably you can go with the 5'6" if you plan is to use it as your low wind board.
The Vanguard have full rails so have almost the same volume on the rails than in the middle of the board.
I was really surprised with the weight of the board the first time I have it on my hands, is really light for a kite version board. I'm going to weight the board with fins and pad installed because a forum member ask me about this........................
The wind forecast looks bad for the weekend but I would try to surf the Vanguard, of course with a rashguard!
I use the WCT medium fins on some of my surfboards and I like them a lot. For my weight the WCT is one of the "recommended" fins for the vanguard but I'm going to try it also with the Mulcoy fins.
I just received my 5'2" Vanguard last week and got my first ride on it this weekend. For reference, I am 180 lb and 5'10".
I got it out in 15 mph winds with a 12m kite and small 1-2 foot swell. The board was plenty big enough for me to kite and I would not want anything larger. The amazing thing about the board is how quick it is to plane - one pump of the legs and you are off to the races. I can't wait to get this board out in some nice size waves.